1. Field
This art is related to an electronic circuit device for controlling a switch which connects a circuit to a power supply.
2. Description of the Related Art
As one of functions for reducing the power consumption of a semiconductor integrated circuit used in an electronic device, there is a power shut-off function. The power shut-off function stops the power supply to a circuit of a predetermined block constituting an electronic circuit device such as a semiconductor integrated circuit. The function can reduce unnecessary power consumption in the standby state of the circuit and increase the time of continuous operation of the electronic device. To stabilize the operation of the circuit, the circuit is normally connected in parallel to a capacitive element for stabilizing a power supply voltage. If the connection between the circuit and the power supply is interrupted, the connection between the capacitive element and the power supply is also simultaneously interrupted. Meanwhile, the circuit and the capacitive element are constantly connected to each other. Thus, if the connection of the circuit to the power supply is interrupted, the capacitive element is discharged by the circuit. When the circuit is reconnected to the power supply, therefore, the capacitive element needs to be charged. This phenomenon causes a delay in the activation of the circuit.
As conventional techniques, there are techniques disclosed in Japanese Unexamined Patent Application Publication Nos. 2001-358294 and 2004-327820. The technique of the former publication turns off a switch connected in series to a capacitive element to prevent the charged capacitive element from being discharged. The technique of the latter publication turns off a switch connected in series to a MOS (Metal Oxide Semiconductor) capacitor to prevent gate leakage caused by the MOS capacitor.